MacBook Pro - Background processes and memory usage

While monitoring my memory usage today, I noticed that that almost an entire gig of my memory was being used when I only had one or two light programs running (MacMail, iChat). Upon checking the activity monitor, I saw that there were quite a few processes running that I did not recognize and that were using quite a bit of memory. Can anyone point me to a resource that could define some of the basic processes that typically run in OS X so that I can begin the task of sorting out which ones I should have running vs which ones could be a problem. I am fairly new to the internal workings of OS X. Any help or advice that people have would be greatly appreciated.

"May the good lord keep the wolves in the hills and the women in our beds."